In a double boiler (bain-marie), melt the chocolate over very low heat, with the butter, coffee, vanilla, and rum or Grand Marnier.

Remove pan from heat and beat in the egg yolks, one at a time.

In a bowl, with a mixer, beat the egg whites with salt, until they are frothy.

Add cream of tartar, and beat the egg whites until they hold soft peaks.

Gently add the sugar and beat for a minute more, or until they hold stiff but not dry peaks.

Fold them gently but thoroughly into the yolk-chocolate mixture.

Pour the mousse into a large serving bowl or into serving cups.

Chill, covered, at least 3 hours or overnight.

For a stronger mousse, omit the extra egg white, which makes the mousse on the light side.

Comments

While chocolate mousse might be light in texture,
it is not a "light" dessert. It can be presented
individually, in a nice cup or fancy glass, or it
can be served in a lovely crystal bowl, as one
spectacular dessert, garnished with dollops of
whipped cream.